J/AJ/147/119 Catalog of sources in the Kepler field of view (Coughlin+, 2014)
Contamination in the Kepler field. Identification of 685 KOIs as false positives
via ephemeris matching based on Q1-Q12 data.
Coughlin J.L., Thompson S.E., Bryson S.T., Burke C.J., Caldwell D.A.,
Christiansen J.L., Haas M.R., Howell S.B., Jenkins J.M.,
Kolodziejczak J.J., Mullally F.R., Rowe J.F.
<Astron. J., 147, 119 (2014)>
=2014AJ....147..119C 2014AJ....147..119C
ADC_Keywords: Stars, double and multiple ; Planets ; Binaries, eclipsing ;
Magnitudes
Keywords: binaries: eclipsing - instrumentation: detectors - planetary systems -
planets and satellites: detection - stars: statistics
techniques: photometric
Abstract:
The Kepler mission has to date found almost 6000 planetary
transit-like signals, utilizing three years of data for over 170000
stars at extremely high photometric precision. Due to its design,
contamination from eclipsing binaries, variable stars, and other
transiting planets results in a significant number of these signals
being false positives (FPs). This directly affects the determination
of the occurrence rate of Earth-like planets in our Galaxy, as well as
other planet population statistics. In order to detect as many of
these FPs as possible, we perform ephemeris matching among all
transiting planet, eclipsing binary, and variable star sources. We
find that 685 Kepler Objects of Interest (KOIs)--12% of all those
analyzed--are FPs as a result of contamination, due to 409 unique
parent sources. Of these, 118 have not previously been identified by
other methods. We estimate that ∼35% of KOIs are FPs due to
contamination, when performing a first-order correction for
observational bias. Comparing single-planet candidate KOIs to
multi-planet candidate KOIs, we find an observed FP fraction due to
contamination of 16% and 2.4% respectively, bolstering the existing
evidence that multi-planet KOIs are significantly less likely to be
FPs. We also analyze the parameter distributions of the ephemeris
matches and derive a simple model for the most common type of
contamination in the Kepler field. We find that the ephemeris matching
technique is able to identify low signal-to-noise FPs that are
difficult to identify with other vetting techniques. We expect FP KOIs
to become more frequent when analyzing more quarters of Kepler data,
and note that many of them will not be able to be identified based on
Kepler data alone.
Description:
NASA's Kepler mission is a 0.95m aperture, optical (420-915nm),
space-based telescope that was launched in 2009.
We employed the following sources to create catalogs of transiting
planets, eclipsing binaries, and other variable stars in the Kepler
field of view.
The list of 5785 Kepler Objects of Interest (KOIs), ranging from KOI
1.01 to 4914.01, available at the NASA Exoplanet Archive
(http://exoplanetarchive.ipac.caltech.edu/) as of 2013 December 18.
These include KOIs detected utilizing up to 12 quarters of data (J. F.
Rowe 2014, in preparation), as well as previous catalogs (Burke 2014,
cat. J/ApJS/210/19; Batalha et al. 2013, cat. J/ApJS/204/24; Borucki
et al. 2011, cat. J/ApJ/728/117, cat. J/ApJ/736/19).
The Kepler eclipsing binary catalog list of 2604 "true" Eclipsing
Binaries found via Kepler data as of 2013 December 18
(http://keplerebs.villanova.edu/). The compilation of the catalog and
derivation of the fit parameters are described in B. Kirk (2013, in
preparation). Previous versions of this catalog are described in
Slawson et al. 2011 (cat. J/AJ/142/160) and Prsa et al. 2011 (cat.
J/AJ/141/83).
J.M. Kreiner's up-to-date database of ephemerids of ground-based
eclipsing binaries as of 2013 December 18
(http://www.as.up.krakow.pl/ephem/). Data compilation and parameter
derivation are described in Kreiner 2004 (cat. J/AcA/54/207).
Ground-based eclipsing binaries found via the TrES survey as detailed
in Devor et al. 2008 (cat. J/AJ/135/850).
The General Catalog of Variable Stars (GCVS) list of all known
ground-based variable stars, published 2013 December
(http://www.sai.msu.su/gcvs/gcvs/). This catalog includes both
eclipsing binaries and other periodic variable stars, such as
pulsators. Catalog compilation is described by Samus et al. (cat.
B/gcvs).
We employed the Kepler Input Catalog (KIC; cat. V/133) and the Kepler
Characteristics Table (http://archive.stsci.edu/pub/kepler/catalogs/)
to obtain additional parameters for each object.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 141 12232 Kepler Objects of Interest (KOI), Kepler
Eclipsing Binaries (KEB), and Ground-based
Eclipsing Binaries (GEB) properties
table2.dat 111 697 The 685 False Positive (FP) KOIs, parents, and
properties
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See also:
B/gcvs : General Catalogue of Variable Stars (Samus+ 2007-2013)
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJ/784/45 : Kepler's multiple planet candidates. III. (Rowe+, 2014)
J/ApJS/210/19 : Kepler planetary candidates. IV. 22 months (Burke+, 2014)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/PASP/124/1279 : Q3 Kepler's combined photometry (Christiansen+, 2012)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/ApJ/728/117 : Kepler planetary candidates. I. (Borucki+, 2011)
J/AJ/142/160 : Kepler Mission. II. 2165 eclipsing binaries (Slawson+, 2011)
J/AJ/135/850 : Properties of eclipsing binaries found in TrES (Devor+, 2008)
J/AcA/54/207 : Ephemerids of eclipsing binaries (Kreiner, 2004)
http://exoplanetarchive.ipac.caltech.edu/ : NASA Exoplanet Archive
http://archive.stsci.edu/kepler/kic10/search.php : KIC search page
http://keplerebs.villanova.edu/ : Kepler Eclipsing Binary Catalog
http://www.sai.msu.su/gcvs/gcvs/ : General Catalog of Variable Stars
http://archive.stsci.edu/pub/kepler/catalogs/ : Kepler Characteristics Table
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Type Source type (KOI, KEB, or GEB) (1)
17- 23 F7.2 --- KOI ? Number of the Kepler Object of Interest
25- 33 I9 --- KEB ? Kepler-based Eclipsing Binary identifier
34 A1 --- --- [-]
35- 37 A3 --- n_KEB Primary or secondary eclipse (G1)
39- 50 A12 --- GEB Ground-based Eclipsing Binary identifier
51 A1 --- --- [-]
52- 54 A3 --- n_GEB Primary or secondary eclipse (G1)
56- 64 I9 --- KIC ? Kepler Input Catalog identifier (V/133)
66- 78 F13.8 d Per Period
80- 91 F12.6 d BJD Barycentric Julian Date of minimum (BJD-2400000)
93- 99 I7 ppm Depth ? Eclipse depth
101-106 F6.3 mag Kpmag ? Kepler magnitude
108-116 F9.6 h RAh Hour of Right Ascension (J2000)
118-126 F9.6 deg DEdeg Declination in decimal degrees (J2000)
128-129 I2 --- Mod0 [2/24]? Season 0 module number
131 I1 --- Out0 [1/4]? Season 0 output number
133-136 I4 --- Row0 [2/1080]? Season 0 row number
138-141 I4 --- Col0 [7/1111]? Season 0 column number
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Note (1): Types of source are defined as:
KOI = Kepler Objects of Interest;
KEB = Kepler Eclipsing Binaries;
GEB with KIC = Ground-based Eclipsing Binaries with Kepler Input Catalog
identifiers;
GEB without KIC = Ground-based Eclipsing Binaries without Kepler Input Catalog
identifiers.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 20 A20 --- Cont Contamination mechanism (1)
22- 28 F7.2 --- KOI False Positive Kepler Object of Interest number
30- 38 I9 --- KIC False Positive Kepler Input Catalog number
40- 51 A12 --- PName Name of the most likely parent (we refer to the
contaminating source as the "parent")
52 A1 --- --- [-]
53- 55 A3 --- n_PName Primary or secondary eclipse (G1)
57- 65 I9 --- PKIC KIC number of the most likely parent
67- 70 A4 --- P1:P2 Period ratio (fraction)
72- 78 F7.1 arcsec Dist [2/43000] Distance between the objects
80- 83 I4 pix oX Offset in row between the objects (R1-R2)
85- 88 I4 pix oY Offset in column between the objects (C1-C2)
90- 94 F5.2 mag Kpmag Kepler magnitude of the most likely parent
96-100 F5.2 mag dmag Magnitude difference between the KOI and the
most likely parent
102-109 E8.2 --- D2/D1 Depth ratio (D2/D1) of the KOI and the most
likely parent
111 I1 --- F [0/3] Unique situation flag (2)
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Note (1): Physical mechanisms of contamination:
Antipodal Reflection = Light is able to reflect off a CCD, then off the Schmidt
corrector plate, and back onto another CCD. Due to the optical design, the
location of the resulting ghost image is antipodal to the parent source.
See Section 2.2 for more details;
Direct PRF = Occurs when the Pixel Response Function (PRF) of two stars
overlap, such that light from a parent star is directly included in one or
more pixels that comprise the optimal photometric aperture of a child
(contaminated target) star. See more details in Section 2.1;
CCD Crosstalk = Electronic crosstalk is a physical effect where the electronic
signal in one wire can electromagnetically induce that signal in other
bundled, parallel wires. Section 2.3 for additional details;
Column Anomaly = The signal from a parent can contaminate a child that lies on
approximately the same column of that CCD, up to the entire range of the
CCD. See Section 2.4 for more details.
Note (2): Flag as follows:
1 = The listed parent is likely not the true physical parent, but another
contaminated object due to the same unobserved physical parent;
2 = The computed depth of the Kepler Object of Interest (KOI) is anomalously
large due to a bad crowding correction value or extreme quarter-to-quarter
depth variations;
3 = The given column anomaly occurs on another output of the same module,
instead of the same output.
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Note (G1): For each eclipsing binary we designated the primary eclipse by
appending "-pri" to the name, and if the time of minimum of the secondary
eclipse was given, we created a separate entry for the secondary eclipse
and appended a "-sec."
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 16-Sep-2014